1. Field of the Invention
This invention relates to an improvement in the see-through type finger touch sensing device which is provided on the display screen and is used for inputting the data in the area designated by finger into the computer system, in more specifically, to a new type touch sensing device which detects change of capacitance of touch electrode due to finger touch using the resonant phenomenon of the resonant circuit.
2. Description of the Prior Arts
A see-through type touch keyboard is well known as the man-machine interface unit which is mounted to the display screen of display unit and is used for inputting the data in the area designated by finger touch to the computer system. For the touch keyboard of this kind, it is important factor to accurately detect the touch condition and various methods have been proposed. As the one of such touch sensing systems, a change of capacitance between the touch electrode and ground by finger touch is detected and this method is explained, for example, in the U.S. Pat. No. 3,482,241 and the U.S. Pat. No. 3,971,013. However, such existing method has disadvantages that a ratio of touch and non-touch conditions (ON-OFF ratio) is insufficient and misoperation occurs easily.